A radiation imaging apparatus measures radiation (X-rays) passing through a subject, and obtains a static image or a moving image of the subject. On this occasion, scattered X-rays and beam hardening are considered as factors which reduce image contrast and precision of measured values and deteriorate image quality. The scattered X-rays, which are generated when X-rays pass through the subject, are mixed with direct X-rays being a net transmission amount, and incident on a detector which detects X-rays. The beam hardening, which occurs when X-rays passes through the subject and a part of energy is absorbed by the subject, causing variations in energy distribution, changes an X-ray absorption coefficient of the subject.
By way of example, there is known a technique for correcting influences of scattered X-rays and beam hardening on measured data in a cone beam CT (e.g., see the patent document 1).